From Geico's Hump Day to Jake from State Farm, the insurance industry spends billions of dollars on advertisements each year. But despite the massive amounts being spent on ads, the percentage of customers shopping for auto insurance has dropped over the past two years, according to a new TransUnion Auto Insurance Shopping Index.

Overall, auto insurance shopping rates are down approximately 3% in the last 12 months, marking a continuation of a downward trend observed over the past two years, as 15.2% and 15.7% of the credit-active population shopped for new auto insurance policies in 2013 and 2012 respectively.

"We are finding that despite billions of dollars being spent on advertising each year, the percentage of consumers shopping for auto insurance has been dropping for approximately the last two years," said Mark McElroy, executive vice president of TransUnion's insurance business unit. "This places additional pressure on insurance carriers as their pool of potential customers declines."